Who are the Houthis in Yemen?

A Saudi-led coalition has launched air strikes on Yemen in an effort to stop the Houthis' advances [AP]

Yemen - The Houthis began as a theological movement preaching peace, but now find themselves at the centre of an international conflict.

After a breathtaking rise to power, a Saudi-led coalition stepped in on March 25, 2015 and began air strikes on Yemen in an effort to stop the Houthis' advances.

The rise of the Shia rebels began to pick up momentum in August, 2014, when thousands of supporters of the movement protested in the streets of the Yemeni capital Sanaa, urging the government to step down.

Among other demands, Houthi leader Abdulmalek al-Houthi requested that fuel subsidies, which had been cut significantly in late July, be reinstated. If the government failed to meet an ultimatum, he said, "other steps" would be taken. The Houthis were also demanding a more representative form of government that would reflect the seats allocated to political groups and independent activists during Yemen's 10-month National Dialogue Conference, which mapped out the political future of Yemen after its 2011 uprising.

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"This government is a puppet in the hands of influential forces, which are indifferent to the rightful and sincere demands of these people," al-Houthi said in his speech, referring to the United States. The rebels subsequently raided key government institutions in the capital.

Yemeni President Abd-Rabbu Mansour Hadi had called for dialogue with the Houthis, inviting the group to join a "unity government", and the two sides ultimately signed a peace deal brokered by the UN envoy to Yemen, Jamal Benomar. It demanded that the Houthis withdraw from Sanaa and cease hostilities in other provinces in exchange for their demands being met. But the rebels did not comply, as their fighters pushed into other provinces, taking over the strategic port city of Hodeida on the Red Sea.

In October, Hadi named the country's envoy to the US, Khaled Bahah, as the new prime minister. The rebels initially welcomed the appointment, but tensions flared in January when a constitution-drafting panel presented the first draft of the constitution. The Houthis rejected terms about dividing the country into six regions.

When Hadi refused to concede, the rebels stormed his palace, galvanising his resignation. Hadi accused the rebels of pressuring him to install affiliate figures in key positions in the government bodies. The Houthis put Hadi, the prime minister and two other ministers under house arrest and in February, declared that Hadi was being replaced with a temporary five-member presidential council.

Hadi fled to Aden on February 21, declaring himself the legitimate president of Yemen. Just over a month later the Saudi-led coalition began bombing the country, giving sanctuary to Hadi in Riyadh.

Officially known as Ansar Allah (Partisans of God), the Houthi rebels began as a theological movement that preached tolerance and peace in the early 1990s, according to Ahmed Addaghashi, a professor at Sanaa University and author of two books on the movement, Houthi Phenomenon and Houthis and Their Political and Military Future.

Addaghashi told Al Jazeera that the Houthi movement originally held a considerably broad-minded educational and cultural vision. A religious group affiliated with the Zaydi sect of Shia Islam, the Houthis maintain a stronghold in the northern province of Saada.

"The group started as a gathering called the 'Believing Youth Forum' in the early nineties," Addaghashi said.

"Then, it fell into internal strife between two lines; the first called for more openness, while the second urged sticking to the traditional legacy of the Shia sect."

The Houthis have doubled their ability to influence the decision-making process. Previously, the Houthis were not an important part of the transitional process, but now no one can bypass them.

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Ironically, he noted, Hussein Bader Addian al-Houthi, the founder of the group, was in favour of the first line. "The movement turned to arms in 2004 on grounds of self-defence when the first war with the government erupted," the professor said.

Addaghashi said that tensions between Yemeni security forces and the Houthis first flared when the group's supporters protested in mosques in the capital, which then-President Ali Abdullah Saleh saw as a challenge to his rule.

Saleh ordered the arrest of some group members, and urged their then-leader, Hussein al-Houthi, to stop the protesters from disturbing worshippers.

"The first war began when Saleh sent some troops to the province of Saada to arrest Hussein, who refused to curb his supporters," Addaghashi said.

Hussein al-Houthi was killed in 2004 after Saleh sent government forces into Saada. The years-long intermittent war ended in a ceasefire agreement in 2010.

In 2011, the Houthis were among many forces that took part in the revolt against Saleh.

The group has been strongly opposed to one of the central recommendations of the National Dialogue Conference: the transformation of Yemen into a federal state of six regions.

Under the proposed reconfiguration, Saada province, which has historically been the Houthis' stronghold, would be linked to the Sanaa region.

The Houthis have demanded a greater share of power in the federal government, and that the north be designated its own region. In documents released by whistle-blowing website WikiLeaks, US defence analysts suggested the Houthis were unlikely to demand independence, and would continue towards their stated aim of regional autonomy.

"The Houthis are capitalising on widespread frustration with the government and the recent rise in fuel prices to rally support and extract political concessions," April Longley Alley, a Yemen specialist with the International Crisis Group, told the AFP news agency last year.

"What is happening now appears to be increasingly dangerous political bargaining as part of the Houthis' bid to become a dominant political force in the north and in the national government."

In their rise to power, the Houthis recorded a series of important victories over government and rival tribal groups.

The Houthis have historically been concerned with reviving Zaydism amid the increasing influence of Salafism. Since Yemen's 2011 uprising, the Houthis appear to have participated in more sectarian conflicts.

A year after the start of the revolt, which led to the overthrow of Saleh, the Houthis besieged a religious school controlled by Salafis in Saada.

The Shia Muslim rebels said the institute was being used to recruit foreign fighters, but the Salafis said the incident was an attempt by the Houthis to strengthen their hold on the province.

Hundreds died in the clashes, which ended when the Salafis agreed to leave the province. Later clashes, in cities closer to the capital, pitted the Houthis against the Islah party and army brigades allied to it.

"The Islah party… fears Ansar Allah will take revenge for [Islah's] participation in the former regime's [Saleh's regime] wars in Saada," Usama Sari, a pro-Houthi journalist, told Al Jazeera.

According to Sari, the Houthis have accused Islah of inciting people against them, and allegedly encouraging some army regiments to fight them.

The governmentsaid it seized arms cargoes originating from Iran that were heading to the rebels in the north, but the Houthis have disputed accusations of foreign help.

Unlike his predecessor, Hadi, who took power in 2012 following Saleh's removal, originally took a less confrontational stance towards the Houthis, prompting the ire of Islamist parties, who accused him of closing his eyes to alleged Houthi crimes.

Mohammed Nasser Ahmed, Hadi's minister of defence, said the country's armed forces were"neutral and stand at an equal distance from everyone".

The Houthis had moved into mainstream politics in Yemen, after holding 35 seats in the National Dialogue Conference.

The political talks brought together 565 delegates from across Yemen's political spectrum, including tribal and religious groups, and independent women's and human rights activists.

Following the Saudi-led intervention, Hadi has called on the Houthis to surrender their weapons and for their leaders to turn themselves in.